Isolation
by piscespen
Summary: The clock is ticking when the TARDIS becomes infected with a lethal alien virus. Can Donna and an ailing Doctor save her before time runs out for them both?


Donna hurries down the corridor towards the medical bay, a cup of plain chamomile tea and a bowl of chicken broth rattling softly on the tray in her hands. She stops in front of the door, eyeing the smooth glass and metal frame. It's so much less inviting than the other doors aboard the TARDIS. She takes a step towards it and it slides aside with a soft burst of air.

She enters the bay, walking past lab tables strewn with odd looking medical instruments and blinking monitors along the way. There are pieces of equipment in varying shapes and sizes and varying states of assembly sat on work benches. Some of them seem to have been long forgotten, gathering dust in corners. Others gleam and look practically new.

She passes something that resembles a giant electron microscope crossed with a blender and several alcoves with little beds inside, huge dark monitor screens built into the walls above them, before the isolation chamber at the very back of the bay finally comes into view.

The isolation chamber looks like any other bedroom save for the slightly opaque glass walls separating it from the rest of the medical bay. The Doctor sits propped up by several pillows on the bed and looks up from the book he's reading as Donna draws closer. He takes off his glasses, laying them aside on the night table, and smiles wanly at her from behind the glass.

He looks terrible; his normally vibrant brown eyes red-rimmed and bruised with dark circles that extend to the hollows of his cheeks. His nose and lips are chapped and sore looking and the rest of his face is so pale, it's practically grey.

"Hi," she says softly, flashing him a sympathetic smile in return, "how are you feeling?"

"A little better today," he says, though he certainly doesn't sound it. His hoarse, raspy voice is fading in and out like a mobile phone in one of those "Can you hear me now?" adverts.

"I brought you something," she says holding up the tray.

The Doctor grimaces slightly. "Not really hungry just now Donna," he says.

"You _have_ to eat," she says, "you'll fade away to nothing if you don't."

"I'm not sure I'd be able to keep it down."

"It's just tea and soup," she says, smiling encouragingly, "very easy on the stomach."

He frowns, clearly unconvinced, but lays aside the bed covers with a small sigh and slowly rises to his feet.

He's wearing the same blue and white pyjama bottoms he's had on for the past three days Donna notes, but he's changed his shirt to a light heather grey tee.

Donna punches a few buttons on the chamber control panel and a small slot appears in the glass, just large enough to slide the tray through to the other side. She has to work a bit to push it past the force field maintaining the integrity of the quarantine.

The Doctor takes the tray and shuffles listlessly back to bed, his normally lithe movements stiff and painful looking.

"You're not feeling better at all are you," Donna says, eyeing him with no small degree of concern.

"Not really no," he admits, "but I will be, in a few more days."

"This is ridiculous," she says, taking a seat beside him in the big comfy orange chair she's been using to sit up with him at night, "you save an entire planet's population from a lethal alien virus with a vaccine made from your own blood and wind up contracting it yourself."

"I did mention that was a possibility when I was making the vaccine, if you recall," he says.

"Well, yeah," Donna says tartly, "but you kind of glossed over just how likely the possibility was, didn't you."

The Doctor's expression becomes somewhat pained at that. "I appreciate the concern Donna," he says, "but honestly, I'll be fine. This virus is no more than a bad case of the flu for me."

"Emphasis on bad," she says with a frown, "and you could have told me you know," she says, her tone softening. "It isn't as if I would have stopped you, but I would have been better prepared for you throwing up for three days straight."

"Sorry," he says, his head falling wearily against the glass between them, "I didn't want to worry you."

"Not telling me things, _that's_ what worries me."

"Right. Noted. Won't happen again."

"Oh eat your soup, you prawn."

He smiles and retrieves the bowl of broth from the tray at the foot of the bed. He gives it a few unenthusiastic twirls with the spoon, before turning a questioning eye on Donna.

"You _need_ to eat," she says flatly. "Honestly, you're such a child sometimes."

He wrinkles his nose at her. "I really wish you'd let me take you home," he says.

"Oh don't start on that again."

"I'm worried about you Donna," he says, "I'm still highly contagious and if a human being were to contract this virus it would be very... bad."

"How bad is very bad?" Donna asks.

"You've heard of the _Ebola Virus_?"

"Ugh, forget I asked," she says, "anyway isn't that the whole point of you locking yourself away in there, to keep me safe."

"The virus is only active for ten days," he says, still trying to convince her. "I'd pick you up again after that."

"I'm not leaving you," Donna says emphatically, "end of discussion."

"Blimey, you're stubborn," he mutters.

"And you still haven't eaten your soup."

A huge gong-like bell splits the air suddenly and Donna's hands instinctively fly to her ears. "What the hell is that?" she cries over the din.

Though she wouldn't have thought it possible, the Doctor's face has grown even paler than it was before. "It's the cloister bell," he says, alarmed.

"The what? What's it mean?"

"Trouble!" he says.

A sudden high-pitched squeal issues from the chamber's control panel. The Doctor snatches his glasses off the night table and rushes over to it.

"What is it?" Donna asks joining him on the other side of the glass. "What's happening?"

The Doctor stares at the panel, reading the data scrolling across its surface with a look of utter disbelief on his face. "Life support systems inside the chamber are failing," he says.

"What's that mean, failing how?"

"It's venting oxygen," he says, looking up just as the overhead lights begin to flicker and go dark, "but why?" he says, as if talking to himself. "It doesn't make any sense."

"You mean you're running out of air?" Donna asks sharply.

"Wait, hang on," he says, appearing not to have heard her.

There's an old-fashioned roll top desk that's practically buried under books in one corner of the room. The Doctor sweeps the books onto the floor with a swipe of his arm and opens the desk to reveal a monitor attached to a swivel arm that's almost exactly like the one in the console room.

He pulls it out, rapidly tapping the touchscreen while Donna leans against the glass watching him.

"No," he breathes, utterly horrified.

"What is it?" Donna anxiously asks. "What's wrong?"

"No, no, no, no," he stammers.

"Doctor!"

"It's the virus," he says, pulling his hands through his hair. "It must have mutated. It's become airborne and it's infected the TARDIS." He looks at her suddenly, his hand flying to the glass. "Donna! You're not safe out there!"

"Well, I can't bloody well climb inside there with you can I?" she cries, suddenly very frightened.

"Bio-suit!" he snaps.

"You what?"

"On the wall behind you. Put it on."

She turns to find a blue jumpsuit made out of some sort of space-age plastic crammed inside a shelf behind her. She yanks it down and struggles into it, fear turning her movements clumsy.

Inside the chamber, the Doctor has returned to the control panel. Donna glances at the panel on her side of the glass and the falling gauges indicating the decreasing oxygen levels. She swallows and wrestles the helmet that's attached to the suit onto her head, zipping up the front of the suit then smoothing the plastic material back down over it to create an airtight seal.

"Okay, I'm covered," she cries, her voice tinny over the transponder built into the clear plastic face screen inside the helmet, "get out of there!"

The Doctor punches a button on the control panel, nothing happens. He tries again, still nothing.

"Doctor!"

"It won't open!" he cries.

"Sonic it then," she yells, rushing over and punching the _Open_ button on her side of the panel several times to no effect.

"I haven't got it on me!"

"What do you mean you haven't got it on you?" she cries, inexplicably furious with him, "you've always got it on you!"

"Yeah, I'm in my jim-jams Donna," he snaps testily, "haven't got any pockets have I?"

He returns to the console monitor inside the desk and Donna runs around to join him, her gloved palms spread out against the glass between them. He furiously taps the screen, growing more frustrated, until with an exasperated grunt his fist finally comes crashing down on it.

"I can't get through to her!" he cries, then resumes his rapid tapping. "She's convinced herself that I'm a threat because of the virus in my system. She's venting the oxygen on purpose."

"So she's trying to kill you," Donna says flatly. "Well, that's just perfect!"

"Course she's not trying to kill me," the Doctor says defensively, "she's confused and frightened. She's just trying to protect herself."

He suddenly falters, his eyes swimming inside their sockets. His knees begin to buckle and he clutches the edge of the desk for support.

"Doctor!" Donna cries, leaping at the glass.

He seems dazed at first, blinking rapidly as his face and neck break out in a cold sweat, but then the confusion is replaced by a look of horrified knowing. He looks up just as a tremendous creaking groan shudders through the entire ship.

"Donna get-" he yells reaching out for her, but whatever else he'd been about to say is lost in the din of the sudden explosion.

…...

Donna awakens in the dark, the smell of ozone hanging heavily in the air. She's still wearing the bio-suit, though it's hard to tell whether it's in one piece or not. She doesn't think she's hurt, but there's something laying on top of her. It's the big comfy orange chair. With some effort she manages to shift it and climb to her knees.

She senses movement, at first she thinks it's vertigo, but then she realises it's the TARDIS. It's drifting through space like a buoy bobbing in the ocean. She closes her eyes, listening. She can still hear the familiar thrum, rising up through the deck plating beneath her, but it's changed somehow. It's weaker, more erratic; almost as if the TARDIS has suffered a heart attack. She climbs to her feet to discover that the floor is listing to one side as well, sloping downwards away from her into the darkness.

"Doctor?" she calls out into the gloom, her arms held out before her, feeling her way through the darkness. The floor is littered with debris. Donna carefully picks her way around it to avoid falling down the gradually steepening slope.

"Doctor?" she calls again, her outstretched hands connecting with something solid in the darkness; the walls of the isolation chamber.

"Doctor!" she cries when she sees him still trapped inside, silently retching in the nearest sloping corner. "Oh my God," she breathes, falling to her knees by the glass wall in front of him.

She watches him silently spewing bile onto the floor, whatever mechanism that had allowed them to talk to each other through the thick glass walls seemingly burnt out. She glances up at the control panel, but it's dark as well, there's no way to tell how much air he might have left, though she suspects not much.

He wipes his mouth with the back of his hand and manages to pull himself up into an almost sitting position, though the effort seems to drain most of his strength. He places his palm flat against the glass and Donna covers it with her own gloved hand. He says something, his mouth moving silently in the burnt out chamber.

_Are you all right?_

Donna nods, feeling tears prick her eyes. "There has to be some sort of, I don't know, emergency override or something!" she shouts back at him.

He shakes his head, his hand sliding lethargically to the floor, as if the effort of holding it up has become too much for him.

_Offline, _he mouths, his eyes sliding shut.

"No, don't!" Donna cries springing forward, both her hands pressed flat against the glass. "Doctor, please, just tell me what to do! I don't know what to do!"

He lifts his head with some effort, staring at her with ancient ageless eyes. _Medical Bay,_ he mouths simply. Then his head falls wearily against the glass between them and his eyes close. They do not open again.

"Wait, what?" Donna yells at him. "I don't understand!" She beats her hands against the glass, sobbing now. "Doctor, what does it mean? I know we're in the medical bay. What _about _the medical bay?!" She falls backwards, tears stinging her eyes as she takes in his silent, unmoving form.

Her jaw sets and she abruptly stands up, angrily blinking the tears away. "All right Donna think," she mumbles impatiently to herself. "Medical bay. What's in a medical bay. Instruments, machines, beds," she shakes her head, changing tack. "What are medical bays used for. Treatment, surgeries, surgical instruments, scalpels," her eyes grow suddenly wide. "Lasers!" she cries in triumph. "Lasers that can cut through glass!"

She flies into the darkness, trying to locate by feel the lab table she'd passed earlier with all the medical instruments on it. Most she finds empty, their contents strewn across the listing floor and sliding away into the darkness. Donna falls to her knees, gathering as many instruments as she can find, quickly picking through them, discarding them one by one when they aren't what she's looking for. She finds a torch and lays it across her lap, the search made all the easier for the added light.

Finally she finds it. It looks like an ordinary dentist's torch, but when she twists one end a telltale beam of light springs out of the other. She twists it a few more notches, watching in satisfaction as the laser beam grows stronger. She twists it as far as it will go and the beam cuts through a bench leg like butter, sending it clattering to the floor with a loud crash.

"Yep, that'll work," she cries, then takes off back into the dark, the torch beam lighting the way before her.

She reaches the burnt out isolation chamber and breathlessly falls to her knees in front of the Doctor's immobile form. She doesn't want to come anywhere near him with the laser, so she crawls on hands and knees to the wall behind him and chooses a suitable spot to cut that's far to the left of his body.

Her hands are trembling, so she lays the torch aside and with a little prayer to whatever gods may be listening, presses the button on the laser scalpel, guiding it with both hands in a rectangular pattern down to the floor.

She tosses the laser aside after burning a suitable wedge into the glass, leaning back on her elbows and kicking with all her might until the thick glass slab splits apart and breaks through to the other side.

She crawls forward into the opening, weak with relief to find the Doctor already starting to come around. He lifts his head and looks at her, wincing slightly as he pushes himself away from the wall. Donna throws her arms around him in a very relieved hug and the Doctor returns it with a slight groan.

"You're hurt?" she asks, suddenly anxious.

"Just a bit sore," he says.

They crawl on hands and knees out of the opening. Donna first, she lingers behind to help the Doctor climb out. He flops onto his back as soon as they're free, breathless and clearly exhausted, Donna kneeling anxiously beside him.

"I am so getting rid of that thing," he says, staring up into the darkness. "It's all stasis fields these days isn't it, but no I had to go old school."

His eyes move to Donna's face. He looks so sick and miserable. She tenderly brushes the hair from his forehead and one side of his mouth quirks into a half-smile.

"Oh well," he says softly, "can't lay about here all day, can I."

He slowly raises himself up off the floor, Donna rising beside him, ready to offer him a hand should he need one. He closes his eyes once he gets to his feet, taking several deep breaths and looking for all the world as if he's about to be sick again.

"All right?" Donna asks.

The Doctor nods. "Yeah," he says, though it seems far from the truth.

"You're getting worse," Donna says, anxiously biting her lower lip.

"It's not me," he says, "it's the TARDIS."

"How do you mean?" Donna asks.

"We're connected, she and I."

"Right telepathically, I remember," Donna says.

"No, but it's more than just that," he says. "Every TARDIS biologically imprints with its Time Lord. It's a symbiotic relationship."

"Meaning?"

"I feel what she feels."

Donna swallows and impulsively places her hands on the Doctor's chest. His hearts are beating out the same anaemic rhythm as the TARDIS.

"And, if the TARDIS dies?" she asks, breaking contact. "What happens to you?"

"Honestly?" the Doctor says with a sigh, "I'm not really sure." He takes her gloved hand in his. "Let's not find out," he says, leading the way onward into the darkness.

…...

"You're not shooting me with that thing Sunshine!" Donna cries, backing away from the Doctor and the hypospray gun in his hand.

"It's got a microscopic needle Donna," he says testily. "It's designed to inject serum directly through the pores of the skin. Trust me, you won't feel a thing."

He's brought them to the lab where he'd been storing the leftover vaccine; kept safe inside one of the refrigerated containment units bolted to the floor. He'd insisted on inoculating Donna the moment they'd arrived.

"Why's it so big then?" Donna cries. "It's like a bloody Uzi!"

The Doctor pauses, eyeing the at best, palm sized device in his hand skeptically. He's dripping with sweat Donna notes, his tee shirt stained in a wide trail down his chest and back. She's never seen him perspire before.

"You're sure it won't hurt," she says, eyeing his ashen face and feeling suddenly silly for making a fuss.

"Cross my hearts," he says.

Donna closes her eyes and feels him raise the hypospray gun to her neck, injecting her directly through the plastic of her bio-suit. She feels a sudden puff of icy air penetrate her skin that lasts for no more than a second, then opens her eyes to find the Doctor smiling wanly at her. She swats his arm in annoyance.

"Oi!" he cries.

"Why didn't you just do that in the first place instead of locking yourself up like a fish in an aquarium for three days, you idiot!" she cries tartly.

"Because, Donna," he snaps back, "the vaccine wasn't designed for use on humans! I'm not sure it'll even work on you, but it's the only thing I could come up with at the spur of the..." he breaks off with a sudden convulsive swallow.

He sways on his feet then bolts for the bin sat beside the lab table. He falls to his knees and vomits into it. Donna rushes to his side, dropping to her knees beside him and slowly rubbing his back as his entire body heaves with the effort to expel the poisonous contents of his stomach. The Doctor's forehead drops forward to rest against the wall. He heaves dryly a few more times, before the sickness passes and he wearily eases himself to a sitting position beside the bin.

Donna rests her gloved hand in his. "I'm sorry," she says softly.

He flashes her a weak smile. "Me too," he says. He eyes the containment units across the room, swallowing in what looks like considerable pain. "There's water in one of those," he says with a nod.

Donna checks each unit until she finds the one that's filled with bottles of water. She removes two and rejoins the Doctor on the floor, handing one of the bottles to him.

"This isn't some weird Martian water is it?" she wryly asks.

The Doctor's mouth quirks fleetingly. "You'd have to check with _Tesco,_" he says.

He gulps a mouthful of water, swirls it around his mouth and spits it out into the bin. Then he takes another long pull from the bottle and swallows it. "Right," he says, wiping some of the sweat from his face with the collar of his shirt, 'let's see if we can't get some of her systems back up and running."

He climbs to his knees, feeling along the wall until he finds what he's looking for. He presses something and an access panel slides away, opening up into some sort of utility conduit inside the wall.

"There should be a torch in one of those drawers," he says, and Donna rifles through each one until she finds it. She switches it on and aims it at the mass of wires inside the conduit so the Doctor can go to work replacing burnt out connections and cobbling wires together with quick deft movements of his fingers.

"Right," he says wearily, "let there be light," and the emergency tract lights above their heads sputter to life, illuminating the bay in a pale blue glow. "Not exactly Broadway is it," the Doctor says, frowning slightly, "but it's the best I can manage under the circumstances." Donna doesn't mind, any light is preferable to stumbling around in the dark.

"Now for a bit of course correction," he says, reaching inside the conduit one more time. The TARDIS begins to slowly right herself, straightening out and eventually slowing to an apparent stop, though Donna knows they're still adrift in space somewhere.

The Doctor lifts his hand out of the conduit and replaces the metal panel with a soft click. "That's all I can do from here," he says, "I'd need to get to the console room to effect anything more permanent."

"Can you fix her?" Donna asks.

He looks at the pale strips of light glowing above their heads. "Navigation and environmental controls are just basic systems. Easy fixes. It's the virus I'm worried about."

"What about the vaccine?" Donna asks. "Will it work on her?"

His eyes turn thoughtful. "It might," he says softly. "If I inject it directly into her Briode Processor then theoretically, the Time Lord DNA in the vaccine should allow me to metabolise the pathogen for her." He suddenly frowns. "Except..." he says, breaking off.

"Except?" Donna asks.

The Doctor sighs. "If I do that, then it'll only strengthen the bond between us. If I can't save her, Donna. If she..." he breaks off, unable to bring himself to even say the word, "then..."

"Then you'll both die," Donna says numbly, a huge black pit opening in her stomach and spiralling down to the floor.

The Doctor takes her gloved hand in his. "It's the only way," he says softly. "She _will_ die if we do nothing."

Donna nods, unable to meet his eyes. "I know," she says simply.

…...

She watches him in silence, moving purposely about the room, a look of determination on his translucently pale face as he plucks the last vial of vaccine from containment. He slips it into the hypospray gun, then opens one of the drawers in the lab table, rifling through it until he finds what he needs; a small cloth pouch attached to a sturdy looking cord. The hypospray gun disappears inside, though the pouch is easily half its size. The Doctor hangs the cord around his neck. Of course he'd have a pocket on a string, Donna thinks, nearly smiling.

Another drawer opens and he removes something that looks like a metal cuff bracelet with some sort of digital display scrolling across its surface. He squints at it, tapping several keys on the display, before rejoining Donna.

"Put this on," he says, though he doesn't exactly give her a choice in the matter, locking the bracelet in place over the sleeve of her bio-suit himself.

"What is it?" Donna asks.

"Temporal shift," he says, "time travel without the TARDIS. The ride may be a bit bumpy, but it'll get you back home in one piece."

Donna snatches her arm away. "I'm not leaving you," she insists again.

The Doctor's expression is grim when he takes her by the shoulders, looking intently at her through the view screen of her helmet. "I know," he says. "You've been exposed to the virus Donna and I am sorry, I am so sorry, but you can't go home."

Donna swallows and nods, her heart fluttering with fear. "What's _this_ for then?" she asks, nodding at the bracelet on her wrist.

"It's an insurance policy," the Doctor says. "The virus's incubation period is ten hours, ten hours in which the first symptoms begin to appear. If anything should happen to me, press the green button on the temporal shift after the ten hours are up and it'll take you home."

"What are you talking about?" she snaps, suddenly angry. "Of course I'm not going home!"

"Donna please, for once don't argue with me!" he cries in exasperation. "If anything happens to me, I need to know that you'll be safe."

"Stop saying that," she desperately cries.

"Listen to me," he says softly, placing his hands on either side of her helmet and forcing her to look him in the eye. "You know I think you're brilliant don't you?"

Donna can't stop the ragged sob that escapes her throat.

"Because you are," the Doctor continues, his own voice choked with emotion. "You are brilliant, Donna Noble, and don't you ever doubt it, not even for one-second. If anything happens to me, promise me you'll go home and go on being brilliant for the rest of your life. Even if it means you have to do it without me."

Donna feels as if she's about to shatter into a million little pieces. "I promise," she chokes brokenly, tears silently spilling from her eyes.

She folds herself into his embrace, shuddering with emotion. The Doctor wraps her in his arms and holds her until she quiets. She can feel the heat coming off of him even through the bio-suit and is suddenly afraid.

"Just so we're clear Spaceman," she says gripping him even more tightly, "I'm not having anything happen to you."

"I'll keep that in mind," the Doctor says and Donna can hear the smile in his voice.

"Make sure you do," she says, and shudders as another thought strikes her. "If I _have _been infected," she says, "when would I start feeling the effects?"

The Doctor stiffens slightly. "Anytime within the next ten hours," he says softly.

"What are the symptoms?"

"Headache, nausea, vomiting," he says, "high fever, delirium, internal bleeding-"

"_Internal bleeding_?!" Donna gasps, horrified.

"Followed by organ failure and death," the Doctor concludes grimly.

"Oh, God," Donna breathes.

"Donna look at me," he says, disengaging from their embrace and holding her at arms length. Donna focuses on his ashen face. "If you _are _infected, then I will do everything in my power to save you. You do know that, don't you?"

"Yes," she says numbly, thinking of her mum and her granddad and how much she'd like to see them again.

The TARDIS shudders, a low creaking groan vibrating through the walls and floor. The Doctor falls to his hands and knees, his nose suddenly bleeding. Donna drops to his side, bracing him when his eyes start to swim and he looks as if he's going to pass out.

"Doctor!" she cries, "What is it?" The shuddering increases, growing in volume and intensity. Donna attempts to staunch the flow of blood that's pouring freely from the Doctor's nose with her glove.

"She," the Doctor gasps, suddenly breathless, "she's losing dimensional integrity."

"What's that mean?"

"We need to get out of here," he cries, staggering to his feet.

They flee the lab to find the rest of the medical bay engulfed in a maelstrom. Donna watches in horror as tables and lab equipment are swept up in a sort of tidal wave of disappearing matter. It rolls towards them, leaving nothing but empty space in its wake.

"This way," the Doctor cries, grabbing her hand.

"What is that thing?" she gasps

"Reverse matter conversion!"

"You what?"

"She can't maintain dimensional transcendence. She's imploding. Losing matter as the space inside her collapses."

_Organ failure_ Donna realises, her heart sinking.

"Like a cascade effect," he cries. "We have to get to the console room. If the wave reaches there..." his voice fades into breathless silence.

"Then, what?" Donna gasps.

"Then she'll just be an empty blue box," the Doctor gasps raggedly, "drifting in space."

They run across the rapidly imploding bay, the matter wave chewing up the space behind them with a thunderous hurricane like roar. She expects the Doctor to swerve when a wall looms ahead of them, but to her surprise he comes to a sudden halt right in front of it instead.

"What are you doing?" she gasps, eyeing the rapidly advancing wave with alarm.

"Shortcut," he says simply, opening something that looks suspiciously like a fuse box hanging in a recess built into the wall.

"Doctor!" Donna cries, flattening herself against the wall's coral surface, closing her eyes as the wave bears down on them.

The partition at her back suddenly falls away and Donna is abruptly falling through empty space into darkness. She screams, but the Doctor suddenly catches her and hauls her the rest of the way over the threshold, slamming the door shut behind them.

…...

A single bare lightbulb hangs from a cord above their heads. The Doctor tugs the chain once and it springs to life, illuminating a tiny room full of doors; doors everywhere, doors of every shape and size covering the walls and ceiling.

Breathless and trembling, his nose caked with dried blood, the Doctor leans heavily against a wall and slides slowly to the floor, his eyes unfocused and heavy. Donna kneels beside him and runs her gloved hand soothingly through his sweat plastered hair.

"You're burning up," she says softly.

The Doctor closes his eyes, letting his head fall back against the door behind him. "I'll be fine," he gasps, "just need a moment to catch my breath."

Donna rests her hand in his, thoughtfully eyeing the doors around them. "What is this place?" she asks, curious despite herself.

The Doctor flashes her a wan smile, "It's an _n-cube_," he says. "Well, technically it's a rhombicuboctahedron, but I won't tell if you don't."

"What's it for?"

"It's a sort of fail-safe system," the Doctor says. "Specifically it's the one place on board the TARDIS where space and time exist in the same dimension."

"Which means what exactly?"

"It's just as big on the outside as it is on the inside," he says. "You can get to any room on board pretty much instantaneously, just by going through one of those doors."

"What, any of them?" Donna cries, incredulous.

The Doctor nods. He points at the inverted door directly above their heads. "The console room," he says.

He climbs to his feet, leaning heavily against the wall of doors at his back. The door to the console room sits about a foot and a half above his head.

"Haven't you got a stepping stool, or something?" Donna asks.

"No," he says a bit sheepishly, "last time I was in here I was taller."

She's not sure what to make of that.

The Doctor gathers his strength for a moment, then stretches to release the latch above his head. The door swings down into the room with a soft creak. He glances at Donna and mops some of the sweat from his face with the collar of his shirt. Then with a determined sweep of his tongue across his chapped lips, he leaps for the open doorway.

Donna rushes forward as he grasps the edge and slowly hauls himself up and over it, having to pause midway through to catch his breath. She watches his legs disappear over the threshold and hears a loud crash a moment later.

"Doctor!" Donna cries in alarm.

"I'm fine. I'm good," comes his somewhat muffled reply. "I'm... a klutz."

His pallid face appears in the doorway, his arm extended towards her. "Grab on," he says.

"Are you sure...?" Donna asks, somewhat hesitantly extending her arm. Next thing she knows she's being hauled towards the open doorway, the Doctor expending what may be the last of his wiry strength in the effort.

She grasps the edge of the threshold, dangling precariously for a moment while the Doctor shifts his grip, then with a final powerful heave he pulls her through, landing on his back with a sharp yelp of pain when Donna lands on top of him.

"Sorry, sorry," she mutters apologetically, quickly scrambling off of him onto her knees.

"Not at all," he says weakly, "I mean, I may throw up on you, but otherwise it's not a problem."

The console room is dark, save for the emergency lights glowing overhead and the central column; its usual shimmering bright blue muted to a sickly yellow-green. The constant thrum of the engines is even more erratic now, weak and thready, as if the TARDIS is going into shock. Donna grimaces slightly at the thought. Her eyes turn to the Doctor, still lying flat on his back on the metal deck grating beside her.

His nose has started bleeding again. He dabs at it lethargically with his grimy fingers. "I'm sorry my nose appears to be running," he says softly, "and I haven't any _Kleenex_. He squints myopically at the crimson streaks staining his fingers. "Odd colour though," he says, "must be the red lights."

Donna frowns at the pale blue emergency lights softly glowing over their heads.

"There aren't any red..." she starts to say, breaking off when the Doctor suddenly shudders, his eyes rolling back into his head.

"Doctor!" Donna cries, springing forward to grip his shoulders in alarm. "Are you all right?"

His teeth are chattering. "Cold," he gasps, "we need to get in out of the snow."

"Snow?' Donna whispers. She studies his ashen face, his eyes half-closed and looking right through her. "Where are you?" she asks him softly, a chasm forming in the pit of her stomach.

"My head. It's splitting," he says, seeming not to hear. "Too many songs inside my head."

Donna grimly presses her lips together and lays her gloved hand on his clammy cheek. The Doctor shivers and flinches away from her outstretched fingers.

He's so hot.

Donna eyes the cloth pouch hanging from his neck. "Doctor," she says calmly, though her heart is skipping like a jackhammer inside her chest, "the Briode Processor. Where is it?"

"They said my song would be ending soon," the Doctor is mumbling deliriously, "maybe they were right."

"Doctor!" Donna cries, taking his face in both her hands. "You need to focus! The Briode Processor. Tell me where it is!"

The Doctor thrashes weakly in her grip, as if his tender skin has become too sensitive to bear any contact. The TARDIS shudders and he groans, curling into a foetal position beside her. His stomach heaves and he spews bile onto the deck plating. It sloughs through the metal grating, dripping down to the sub-flooring below.

"Could I have a drink?" he murmurs. "I'm so thirsty." She shudders a second time and he screws himself into an even tighter ball, gagging dryly. "No more lime-soda though," he says, swallowing painfully, "I don't think it agrees with me."

"Doctor please, we're running out of time," Donna pleads with him. "You have to tell me where the Briode Processor is."

"What, aboard the TARDIS you mean?" the Doctor asks, his eyes blinking sluggishly.

"Yes!" Donna cries desperately. "Where is it?"

"It's in the console room."

The shuddering abruptly increases, a growing tremor vibrating up from the floor and spreading through the walls like an earthquake. Donna steadies the Doctor and looks up to find the edges of the console room beginning to dissipate into nothingness.

"Oh God," she breathes. She squats down beside him, their faces separated by inches and the plastic view screen of her helmet. "_Where_ in the console room?" she asks.

The Doctor's face is pinched with pain, his eyes bleary and barely open. Donna tenderly brushes his damp cheek with the back of her gloved hand and he reluctantly focuses on her face. "Help me," she pleads softly.

He blinks, seeming to rouse himself with some effort at her words. "Access panel in the sub-flooring," he gasps raggedly, his eyes regaining some of their focus, "directly below the central column."

Donna slips the pouch off his neck and springs to her feet. "Oh you're leaving?" the Doctor mumbles after her, as she sprints up the ramp towards the console. "Right, I'll just wait for the bus back here then shall I?"

…...

Donna stumbles, falling to her knees as the TARDIS begins to shudder more violently, the pouch nearly slipping from her fingers in the process. She tightens her grip and pries a section of metal grating from the floor with trembling fingers. The walls continue to disappear around her, shimmering and fading into nothingness as if they're being eaten away by some invisible parasite. In a way Donna supposes, they are.

She swings her legs around and drops through the opening in the grate to the sub-flooring some three feet below. Liquid filled tubes and brightly coloured wires meander in a tangle around glowing roundels nestled in a kind of mosaic pattern on the floor. It's oddly beautiful Donna thinks, as she quickly picks her way through the maze of living circuitry, her steps made all the more difficult due to the deliriously thrashing ship.

The circuitry becomes more sparse, disappearing all together around the central column where a series of access panels in varying shapes and sizes sit instead. For the protection of the truly sensitive systems Donna supposes, as she quickly lifts the panel directly below the central column up and out of the small space. Inside is something that looks very much like a brain encased in plastic wrap, glowing the same sickly yellow-green as the column; tubes and wires branch out from it like arteries, disappearing into darkness beneath the floor.

"This must be the place," Donna mumbles to herself and opens the pouch.

She clutches the hypospray gun, the TARDIS bucking and shuddering around her. A particularly violent shake and she bobbles it, catching it in midair with her other hand before it can hit the floor. Donna bites her bottom lip and with trembling fingers plunges the hypospray into the brain-like mass inside the floor panel. She discharges the entire contents of the vaccine vial into it, silently praying that she hasn't given the TARDIS some sort of fatal overdose.

No sooner does she finish then the shuddering abruptly increases, growing more violent with each passing second. Donna cries out when the TARDIS suddenly pitches, sending her tumbling into a retaining column. The glowing roundel mosaic flickers and sparks, filling the sub-chamber with smoke. Donna coughs and crawls on hands and knees to the Briode Processor. She watches in horror as a thick tarry substance flows through the artery tubes, engulfing the brain and turning it pitch black.

"No," Donna breathes, watching the tarry substance migrating to the central column; slowly flowing into it like a sinister black tide.

She hears movement on the deck plating above and gropes her way through the billowing smoke back to the open grate. She finds a step ladder and scrambles back up it into the console room.

The walls are gone, crumbling into the empty blackness of space. As Donna watches the outer edges of the floor begin to fade, disintegrating inwards towards the central console. The Doctor sits breathlessly swaying on his knees, clinging to the console as if he can somehow hold off the matter wave through sheer force of will alone.

"Doctor!" Donna cries, falling to her knees beside him.

His eyes are closed. The room steadily darkens as the rising black tide fills the central column and the TARDIS abruptly rolls in response, plummeting through space. Donna cries out as she crashes against the console. Beside her the Doctor groans, his back arching in obvious pain. Donna extends her hand towards him and he suddenly grabs her wrist, his eyes opening wide. They're completely obscured behind a thick film of black tar.

Donna screams despite herself, instinctively trying to escape his grasp, but the Doctor's other hand snatches her free wrist and holds it in a surprisingly strong grip. Donna continues to struggle for a moment, then sags as a subtle malaise dissipates from her body; the beginnings of a dull headache fading away like footprints in the sand.

The Doctor abruptly releases her, falling onto his hands and knees. His body trembles and black tar begins to seep from his eyes, his nose, his mouth, running down his face and dripping through the floor grating like a thick dark waterfall. His stomach heaves and he vomits more of the stuff through the grate and onto the sub-flooring below.

Donna looks on in wide-eyed horror, hugging the console as the TARDIS convulses. Her eyes stray to her wrists and she suddenly remembers what the Doctor had said earlier in the lab about metabolising the pathogen. All at once, she understands. He hadn't been attacking her when he'd grabbed her, he'd been _saving_ her. Drawing the virus out of both Donna and the TARDIS and into himself.

"Oh my God," she whispers.

The Doctor convulses, expelling black poison across the deck plating like a drowning man choking in a dark sea, while the matter wave relentlessly chews its way across the floor, sweeping towards the console like a blanket of marching carpenter ants.

Smoke billows up through the deck plating from the sub-chambers where the burnt out roundels flicker and spark. The blue emergency lights sputter, blinking out one by one. Something explodes overhead, raining sparks down on them. The Doctor shivers as the last remnants of black tar dribble sluggishly down his face. His eyes roll back into his head and the TARDIS comes to an abrupt bone-jarring halt as he crumples bonelessly to the floor. Donna screams, the sudden jolt sending her sprawling to the floor.

She lays there, panting breathlessly in the sudden stillness. The utter silence eerie after the din of the last few moments. All the emergency lights save one have gone out. She watches it sputter through the darkness and gradually dissipating smoke.

There's no sign of the matter wave, though it's easy enough to make out the path of destruction its left in its wake. The central console and the deck plating immediately surrounding it are still intact, but everything else is just empty space. It's like in cartoons when a tree has been cut down but somehow a single branch remains magically suspended in mid air.

Donna swallows, afraid to move. Her eyes fall on the Doctor's unmoving form, lying on his stomach a few feet away. His face turned towards her, deathly pale in the flickering light.

"D… Doctor," she calls out breathlessly to him. There's no response. She crawls towards him, hugging the floor in case her movements somehow upset the platform's delicate balance.

"Doctor," she says, crouching beside him, her hand on his damp back, "wake up."

His body has begun to cool. She rolls him over and presses her head to his motionless chest, but hears nothing through the helmet's audio amplifier, no breath, no sign of either heart beating.

"Oh no," she whispers, "oh please." She chafes his cheek with the edge of her glove, tears suddenly stinging her eyes. There's no response. The Doctor's limp body is still and silent, completely devoid of the manic energy that usually fuels it.

"Don't do this to me Spaceman." Donna pleads with him. "Don't you dare do this to me!" She glances up at the empty central column. It's dark and motionless, the constant thrumming heartbeat of the TARDIS deafening in its silence.

"Doctor!" she yells brokenly, sobbing now, shaking his unresponsive body, "wake up!" She gathers his damp shirt in her fists, desperately pleading with him to wake up, shouting at him to come back, but wherever he's gone it's beyond his ability to hear.

She falls back against the deck plating, hugging herself as great shuddering sobs grip her body. Her helmet scrapes the metal grating as she folds herself into a wounded trembling ball. "Please, don't leave me alone," she whispers desolately.

Eventually Donna's sobs become less fitful, quieting to sluggish tears and a great weariness descends on her. She lays on the deck plating staring at the Doctor's body in silence. Her eyes stray to the temporal shift blinking on her wrist. She wonders if it's powerful enough to transport both of them. She can't just leave him here, drifting alone and forgotten on the outer reaches of space. Though knowing him he'd probably prefer it that way. At one with his beloved TARDIS for all eternity, together in death as they were in life. Donna takes no comfort in the thought.

She abruptly sits up, sniffing through her tears. She caresses the Doctor's waxen cheek, pulling his head onto her lap. "You idiot," she murmurs fondly, pulling her fingers through his hair, fat tears slowly rolling down her cheeks.

The darkness around her abruptly brightens, the sub-flooring beginning to glow with shimmering blue light. Pale at first, it grows in intensity until bright azure shafts of light pierce the metal grating like stardust. Donna watches in wonder as the glow sweeps through the sub-chambers beneath the console like blue fire and the room slowly begins to reconstitute itself, the familiar coral formations rebuilding themselves; the walls and floor reforming like grains of sand filling an hourglass.

The central column leaps to life, glowing a healthy aquamarine and a glorious thrumming hum reverberates up through the sub-flooring, settling into the walls with a strong familiar rhythm that makes the hairs on the backs of Donna's arms stand up on end. The Doctor inhales and opens his eyes, blinking up at her through gummy eyelashes. Donna gasps, caressing his face, her eyes brimming with relieved tears. The Doctor smiles at her, clearly exhausted but no longer suffering the virus's ill effects.

"It's all right," he murmurs softly, "you can take the suit off now. The virus is gone."

Donna unzips the plastic coverall, shrugging halfway out of it, the sleeves and helmet slipping to the floor behind her. She lays her hands on the Doctor's face, tenderly caressing it, running her fingers across the stubble on his cheeks and chin. The Doctor smiles, covering one of her hands with his own.

"Oh I missed that," he says, closing his eyes.

"What?" Donna asks.

"The touch of your hand," he says softly.

Donna smiles, covering his cheeks and forehead with relieved kisses, the salt from her tears mingling with them and falling onto his face. The Doctor smiles. He doesn't seem to mind.

END


End file.
